In assembling various elements on an e.g. endless web to make personal care articles, it is highly desirable to have a real-time inspection of various aspects of the articles being fabricated, including inspection of the articles at one or more locations on the fabrication line, as the articles are being fabricated and before fabrication is complete.
In the personal care article industry, it is known to use optical brighteners to mark components or portions of elements which form such articles in a fabrication line. When such optical brighteners are properly selected, properly applied, and properly positioned, the articles can be illuminated with ultraviolet light and/or visible light. Ultraviolet and visible light sensors can sense the optical brighteners so illuminated, and can thus record the positions, or relative positions, of components carrying such optical brighteners in such personal care articles. While some article elements can thus be detected, to applicants' knowledge, it is not known to employ such procedures to assess presence and quality of adhesive or other bonds or bonding in the context of a personal care article.
In addition, applicants are aware that some, but not necessarily all, hot melt adhesives inherently fluoresce under ultraviolet light. However, applicants are not aware of any use of such property for detecting relative positioning of elements.
In other methods of assessing or predicting product quality, structural elements such as notches, slits, slots, protrusions, depressions, or holes or the like are formed in the web of personal care articles, thus to provide a detectable structural feature which can be used to sense location of an element.
A region of magnetic discontinuity, electromagnetic discontinuity, or any combination thereof may also be used with suitable sensors of magnetic properties to show the positions of components of respective personal care articles.
The above methods of assessing or predicting product quality require modifying the personal care articles specifically for the purpose of being able to sense or detect the parameters of interest, such as for example using additional material such as an optical brightener, or a magnetic additive, or modifying the structure of the personal care articles, in order to create an element detectable by the sensors selected for the detection function. Such modifications increase the cost of personal care articles, in addition to bearing the cost of the actual detection. Further, use of such additional material, elements, or features includes the risk that the additional material, elements, or features, may be misplaced in the web, or on the respective web element, and thus give a false reading to the sensing system. There is also the risk that such modification to the product or product component may interfere with either the intended use of the personal care article or the safety of a person using the personal care article for the intended use.
It would be desired that no such additional material element, or feature, need be incorporated into or added to any element or feature of the articles being fabricated.